DNS Zones

DNS Zones (/dns-zones) is for a domain you want this server to answer DNS for, but not to host a website for.

A domain added here gets a BIND zone and nothing else: no document root, no vhost, no PHP pool, no certificate, no mailbox. That is the point — a domain whose site is hosted elsewhere, or one you have bought and not built anything on yet, still needs somewhere to answer for it, and creating a website you will never use just to edit an MX record leaves empty directories and unused pools behind.

The records inside the zone are edited with the ordinary DNS Zone Editor.

A DNS-only zone counts against your plan's domain allowance. Subdomains inside a zone do not — they are records in a zone you already have.